Neural dynamics of pain modulation by emotional valence.

Definitions of human pain acknowledge at least two dimensions of pain, affective and sensory, described as separable and thus potentially differentially modifiable. Using electroencephalography, we investigated perceptual and neural changes of emotional pain modulation in healthy individuals. Painful electrical stimuli were applied after presentation of priming emotional pictures (negative, neutral, positive) and followed by pain intensity and unpleasantness ratings. We found that perceptual and neural event-related potential responses to painful stimulation were significantly modulated by emotional valence. Specifically, pain unpleasantness but not pain intensity ratings were increased when pain was preceded by negative compared to neutral or positive pictures. Amplitudes of N2 were higher when pain was preceded by neutral compared to negative and positive pictures, and P2 amplitudes were higher for negative compared to neutral and positive pictures. In addition, a hierarchical regression analysis revealed that P2 alone and not N2, predicted pain perception. Finally, source analysis showed the anterior cingulate cortex and the thalamus as main spatial clusters accounting for the neural changes in pain processing. These findings provide evidence for a separation of the sensory and affective dimensions of pain and open new perspectives for mechanisms of pain modulation.

Effects of spatial location on distractor interference.

When target and distractor stimuli are close together, they activate the same neurons and there is ambiguity as to what the neural activity represents. It has been suggested that the ambiguity is resolved by spatial competition between target and nontarget stimuli. A competitive advantage is conveyed by bottom-up biases (e.g., stimulus saliency) and top-down biases (e.g., the match to a stored representation of the target stimulus). Here, we tested the hypothesis that regions with high perceptual performance may provide a bottom-up bias, resulting in increased distractor interference. Initially, we focused on two known anisotropies. At equal distance from central fixation, perceptual performance is better along the horizontal than the vertical meridian, and in the lower than in the upper visual hemifield. Consistently, interference from distractors on the horizontal meridian was greater than interference from distractors on the vertical meridian. However, distractors in the lower hemifield interfered less than distractors in the upper visual hemifield, which is contrary to the known anisotropy. These results were obtained with targets and distractors on opposite meridians. Further, we observed greater interference from distractors on the meridians compared with distractors on the diagonals, possibly reflecting anisotropies in attentional scanning. Overall, the results are only partially consistent with the hypothesis that distractor interference is larger for distractors on regions with high perceptual performance.

Color category and inter-item interaction influence color working memory codependently.

Our brains do not always encode visual information in a veridical way. Visual working memory (WM) for features such as color can be biased. WM bias comes from several sources. Category priors can lead to WM bias. For example, color WM is biased toward or away from category prototypes. In addition to category knowledge, contextual factors can induce and modulate WM bias; however, these biases of different sources have usually been investigated independently with different tasks. The present study sought to explore how color WM is influenced by both color category and concurrent distractor. Specifically, we asked participants to retain two color items in WM to investigate how the WM representation of the target color is biased by learned category knowledge and contextual inter-item interactions. Our study found that the WM representation of the target color is biased toward or away from the category prototypes and away from the distractor color that is simultaneously held in WM, indicating that both color category and concurrent distractor bias color WM. More importantly, the weight of these two biases depends on the specific color category, suggesting that category priors and inter-item interaction biases are not simply additive but flexible. Furthermore, we revealed that both types of biases arise from perceptual processes.

Presaccadic preview shapes postsaccadic processing more where perception is poor.

The presaccadic preview of a peripheral target enhances the efficiency of its postsaccadic processing, termed the extrafoveal preview effect. Peripheral visual performance-and thus the quality of the preview-varies around the visual field, even at isoeccentric locations: It is better along the horizontal than vertical meridian and along the lower than upper vertical meridian. To investigate whether these polar angle asymmetries influence the preview effect, we asked human participants to preview four tilted gratings at the cardinals, until a central cue indicated which one to saccade to. During the saccade, the target orientation either remained or slightly changed (valid/invalid preview). After saccade landing, participants discriminated the orientation of the (briefly presented) second grating. Stimulus contrast was titrated with adaptive staircases to assess visual performance. Expectedly, valid previews increased participants' postsaccadic contrast sensitivity. This preview benefit, however, was inversely related to polar angle perceptual asymmetries; largest at the upper, and smallest at the horizontal meridian. This finding reveals that the visual system compensates for peripheral asymmetries when integrating information across saccades, by selectively assigning higher weights to the less-well perceived preview information. Our study supports the recent line of evidence showing that perceptual dynamics around saccades vary with eye movement direction.

Different temporal dynamics of foveal and peripheral visual processing during fixation.

Humans explore visual scenes by alternating short fixations with saccades directing the fovea to points of interest. During fixation, the visual system not only examines the foveal stimulus at high resolution, but it also processes the extrafoveal input to plan the next saccade. Although foveal analysis and peripheral selection occur in parallel, little is known about the temporal dynamics of foveal and peripheral processing upon saccade landing, during fixation. Here we investigate whether the ability to localize changes across the visual field differs depending on when the change occurs during fixation, and on whether the change localization involves foveal, extrafoveal processing, or both. Our findings reveal that the ability to localize changes in peripheral areas of the visual field improves as a function of time after fixation onset, whereas localization accuracy for foveal stimuli remains approximately constant. Importantly, this pattern holds regardless of whether individuals monitor only foveal or peripheral stimuli, or both simultaneously. Altogether, these results show that the visual system is more attuned to the foveal input early on during fixation, whereas change localization for peripheral stimuli progressively improves throughout fixation, possibly as a consequence of an increased readiness to plan the next saccade.

Alpha oscillations during visual selective attention are aberrant in youth and adults with cerebral palsy.

Our understanding of the neurobiology underlying cognitive dysfunction in persons with cerebral palsy is very limited, especially in the neurocognitive domain of visual selective attention. This investigation utilized magnetoencephalography and an Eriksen arrow-based flanker task to quantify the dynamics underlying selective attention in a cohort of youth and adults with cerebral palsy (n = 31; age range = 9 to 47 yr) and neurotypical controls (n = 38; age range = 11 to 49 yr). The magnetoencephalography data were transformed into the time-frequency domain to identify neural oscillatory responses and imaged using a beamforming approach. The behavioral results indicated that all participants exhibited a flanker effect (greater response time for the incongruent compared to congruent condition) and that individuals with cerebral palsy were slower and less accurate during task performance. We computed interference maps to focus on the attentional component and found aberrant alpha (8 to 14 Hz) oscillations in the right primary visual cortices in the group with cerebral palsy. Alpha and theta (4 to 7 Hz) oscillations were also seen in the left and right insula, and these oscillations varied with age across all participants. Overall, persons with cerebral palsy exhibit deficiencies in the cortical dynamics serving visual selective attention, but these aberrations do not appear to be uniquely affected by age.

Knowing where to go: Spatial memory guides eye and body movements in a naturalistic visual search task.

Most research on visual search has used simple tasks presented on a computer screen. However, in natural situations visual search almost always involves eye, head, and body movements in a three-dimensional (3D) environment. The different constraints imposed by these two types of search tasks might explain some of the discrepancies in our understanding concerning the use of memory resources and the role of contextual objects during search. To explore this issue, we analyzed a visual search task performed in an immersive virtual reality apartment. Participants searched for a series of geometric 3D objects while eye movements and head coordinates were recorded. Participants explored the apartment to locate target objects whose location and visibility were manipulated. For objects with reliable locations, we found that repeated searches led to a decrease in search time and number of fixations and to a reduction of errors. Searching for those objects that had been visible in previous trials but were only tested at the end of the experiment was also easier than finding objects for the first time, indicating incidental learning of context. More importantly, we found that body movements showed changes that reflected memory for target location: trajectories were shorter and movement velocities were higher, but only for those objects that had been searched for multiple times. We conclude that memory of 3D space and target location is a critical component of visual search and also modifies movement kinematics. In natural search, memory is used to optimize movement control and reduce energetic costs.

Relevance of pre-stimulus oscillatory activity for the perceived valence of emotional facial expressions.

The interpretation of emotional facial expressions is crucial in everyday social interactions, and rapid processing of these expressions is necessary. Although extensive research has shed light on the mechanisms involved in facial expression processing, there is limited research on the potential role of the state of neural activity that directly precedes the occurrence of a face. Here, we investigated the potential modulatory role of pre-stimulus oscillatory activity in emotional facial expression processing. We tested emotional facial processing in two experiments, one utilizing artificial and the other natural facial expressions. The participants had to evaluate the emotional valence of the presented ambiguous facial expressions. In a univariate analysis, differences in the oscillation activity of the later rated valence of the faces were observed in both experiments, and these differences were observed even before the presentation of the facial expressions. Importantly, two different multivariate approaches directly supported the relevance of pre-stimulus oscillatory activity by exclusively using pre-stimulus oscillatory data to predict the perceived valence of the latter rated facial expression across the two experiments within as well as across subjects. The behavioral data shows the often observed negativity bias, i.e. ambiguous faces resulted in the tendency to rate them as negative. This negativity bias was related to neural activity modulations in the pre-stimulus period and also within post-stimulus processing related activity. These findings underscore the significance of pre-stimulus oscillatory activity in facial expression processing, indicating a functional role of ongoing neural states that affects the processing of facial expressions and constitute a basis for the well described negativity bias.

Dissociable neuronal mechanism for different crossmodal correspondence effects in humans.

Crossmodal correspondences (CMCs) refer to associations between seemingly arbitrary stimulus features in different sensory modalities. Pitch­size correspondences refer to the strong association of e.g., small objects with high pitches. Pitch­elevation correspondences refer to the strong association of e.g., visuospatial elevated objects with high pitches. We used functional magnetic resonance imaging (fMRI) to study the neural components, which underlie the CMCs in pitch­size and spatial pitch­elevation. This study focuses on answering the question of whether or not different CMCs are driven by similar neural mechanisms. The comparison of congruent against incongruent trials allows the estimation of CMC effects across different CMCs. The analysis of the measured neural activity in different CMCs strongly pointed toward different mechanisms which are involved in the processing of pitch­size and pitch­elevation correspondences. Differential, whole brain effects were observed within the superior parietal lobule (SPL), cerebellum and Heschls' gyrus (HG). Further, the angular gyrus (AnG), the intraparietal sulcus (IPS) and anterior cingulate cortex (ACC) were engaged in processing the CMCs but showed different effects for processing congruent compared to incongruent stimulus presentations. Within pitch­size significant effects in the AnG and ACC were found for congruent stimulus presentations whereas for pitch­elevation, significant effects in the ACC and IPS were found for incongruent stimulus presentations. In summary, the present results indicated differential neural processing in different simple audio­visual CMCs.

Enhanced audiovisual associative pair learning in migraine without aura in adult patients: An unexpected finding.

BACKGROUND: Altered sensory processing in migraine has been demonstrated by several studies in unimodal, and especially visual, tasks. While there is some limited evidence hinting at potential alterations in multisensory processing among migraine sufferers, this aspect remains relatively unexplored. This study investigated the interictal cognitive performance of migraine patients without aura compared to matched controls, focusing on associative learning, recall, and transfer abilities through the Sound-Face Test, an audiovisual test based on the principles of the Rutgers Acquired Equivalence Test. MATERIALS AND METHODS: The performance of 42 volunteering migraine patients was compared to the data of 42 matched controls, selected from a database of healthy volunteers who had taken the test earlier. The study aimed to compare the groups' performance in learning, recall, and the ability to transfer learned associations. RESULTS: Migraine patients demonstrated significantly superior associative learning as compared to controls, requiring fewer trials, and making fewer errors during the acquisition phase. However, no significant differences were observed in retrieval error ratios, generalization error ratios, or reaction times between migraine patients and controls in later stages of the test. CONCLUSION: The results of our study support those of previous investigations, which concluded that multisensory processing exhibits a unique pattern in migraine. The specific finding that associative audiovisual pair learning is more effective in adult migraine patients than in matched controls is unexpected. If the phenomenon is not an artifact, it may be assumed to be a combined result of the hypersensitivity present in migraine and the sensory threshold-lowering effect of multisensory integration.

The proactive and reactive mechanisms of learned spatial suppression.

Selection history refers to the notion that previous allocations of attention or suppression have the potential to elicit lingering and enduring selection biases that are isolated from goal-driven or stimulus-driven attention. However, in the singleton detection mode task, manipulating the selection history of distractors cannot give rise to pure proactive inhibition. Therefore, we employed a combination of a working memory task and a feature search mode task, simultaneously recording cortical activity using EEG, to investigate the mechanisms of suppression guided by selection history. The results from event-related potential and reaction times showed an enhanced inhibitory performance when the distractor was presented at the high-probability location, along with instances where the target appeared at the high-probability location of distractors. These findings demonstrate that a generalized proactive inhibition bias is learned and processed independent of cognitive resources, which is supported by selection history. In contrast, reactive rejection toward the low-probability location was evident through the Pd component under varying cognitive resource conditions. Taken together, our findings indicated that participants learned proactive inhibition when the distractor was at the high-probability location, whereas reactive rejection was involved at low-probability location.

High segregation and diminished global integration in large-scale brain functional networks enhances the perceptual binding of cross-modal stimuli.

Speech perception requires the binding of spatiotemporally disjoint auditory-visual cues. The corresponding brain network-level information processing can be characterized by two complementary mechanisms: functional segregation which refers to the localization of processing in either isolated or distributed modules across the brain, and integration which pertains to cooperation among relevant functional modules. Here, we demonstrate using functional magnetic resonance imaging recordings that subjective perceptual experience of multisensory speech stimuli, real and illusory, are represented in differential states of segregation-integration. We controlled the inter-subject variability of illusory/cross-modal perception parametrically, by introducing temporal lags in the incongruent auditory-visual articulations of speech sounds within the McGurk paradigm. The states of segregation-integration balance were captured using two alternative computational approaches. First, the module responsible for cross-modal binding of sensory signals defined as the perceptual binding network (PBN) was identified using standardized parametric statistical approaches and their temporal correlations with all other brain areas were computed. With increasing illusory perception, the majority of the nodes of PBN showed decreased cooperation with the rest of the brain, reflecting states of high segregation but reduced global integration. Second, using graph theoretic measures, the altered patterns of segregation-integration were cross-validated.

Perceptual training improves audiovisual integration by enhancing alpha-band oscillations and functional connectivity in older adults.

Numerous studies on perceptual training exist, however, most have focused on the precision of temporal audiovisual perception, while fewer have concentrated on ability promotion for audiovisual integration (AVI). To investigate these issues, continuous 5-day audiovisual perceptual training was applied, during which electroencephalography was performed in response to auditory-only (A), visual-only (V) and audiovisual (AV) stimuli before and after training. The results showed that the perceptual sensitivity was greater for training group than for control group and was greater in the posttest than in the pretest. The response to the AV stimulus was significantly faster in the posttest than in the pretest for the older training group but was significantly greater for A and V stimuli for the younger training group. Electroencephalography analysis found higher P3 AVI amplitudes [AV-(A + V)] in the posttest than in the pretest for training group, which were subsequently reflected by an increased alpha (8-12 Hz) oscillatory response and strengthened global functional connectivity (weighted phase lag index). Furthermore, these facilitations were greater for older training groups than for younger training groups. These results confirm the age-related compensatory mechanism for AVI may be strengthened as audiovisual perceptual training progresses, providing an effective candidate for cognitive intervention in older adults.

EEG Analyses of visual cue effects on executed movements.

BACKGROUND: In electroencephalographic (EEG) or electrocorticographic (ECoG) experiments, visual cues are commonly used for timing synchronization but may inadvertently induce neural activity and cognitive processing, posing challenges when decoding self-initiated tasks. NEW METHOD: To address this concern, we introduced four new visual cues (Fade, Rotation, Reference, and Star) and investigated their impact on brain signals. Our objective was to identify a cue that minimizes its influence on brain activity, facilitating cue-effect free classifier training for asynchronous applications, particularly aiding individuals with severe paralysis. RESULTS: 22 able-bodied, right-handed participants aged 18-30 performed hand movements upon presentation of the visual cues. Analysis of time-variability between movement onset and cue-aligned data, grand average MRCP, and classification outcomes revealed significant differences among cues. Rotation and Reference cue exhibited favorable results in minimizing temporal variability, maintaining MRCP patterns, and achieving comparable accuracy to self-paced signals in classification. COMPARISON WITH EXISTING METHODS: Our study contrasts with traditional cue-based paradigms by introducing novel visual cues designed to mitigate unintended neural activity. We demonstrate the effectiveness of Rotation and Reference cue in eliciting consistent and accurate MRCPs during motor tasks, surpassing previous methods in achieving precise timing and high discriminability for classifier training. CONCLUSIONS: Precision in cue timing is crucial for training classifiers, where both Rotation and Reference cue demonstrate minimal variability and high discriminability, highlighting their potential for accurate classifications in online scenarios. These findings offer promising avenues for refining brain-computer interface systems, particularly for individuals with motor impairments, by enabling more reliable and intuitive control mechanisms.

The influence of task-irrelevant color perception on flanker task performance: Insights from behavioral and ERP data.

Perception of color as a task-relevant stimulus can affect cognition and behavior in the flanker task; however, it remains unclear whether it has the same impact when it is a task-irrelevant stimulus dimension. To this end, we applied four-letter flanker tasks with or without colored (red/blue) to 23 healthy young adults, while recording the event-related potentials (ERPs) and behavioral performance. The flanker task included four kinds of color types: non-color letter (NC), all color letter (AC), flanker color letter (FC), and target color letter (TC), each flanker task included congruent and incongruent conditions. The behavioral data demonstrated the classic conflict effect across all color types of flanker tasks in both reaction times (RTs) and accuracy, the significant interaction and main effect of color type factors were only observed in accuracy. The ERP results showed significant interaction between conflict factor (congruent, incongruent) and color type (NC, AC, FC, and TC), and the color type factor enhanced the fronto-central P2 (180-200 ms), descended the fronto-centro-parietal N2b (260-320 ms), and increased the fronto-central P3b (360-520 ms). The fronto-central P2 and the fronto-central P3b were larger for TC than NC, AC, and FC in the congruent condition, while the fronto-central P3b was smaller for NC than AC, FC, and TC in the incongruent condition. Furthermore, the fronto-centro-parietal N2b was decreased successively in NC, AC, FC, and TC in both congruent and incongruent conditions. Overall, our findings suggested that the task-irrelevant stimuli dimension of color can capture some attentional resources and is affected by the location of color (target/flanker) and the type of task trial (congruent/incongruent) in the flanker task.

Direction-selective adaptation from implied motion in infancy.

We investigated whether adaptation from implied motion (IM) is transferred to real motion using optokinetic nystagmus (OKN) in infants. Specifically, we examined whether viewing a series of images depicting motion shifted infants' OKN responses to the opposite direction of random dot kinematograms (RDKs). Each RDK was presented 10 times in a pre-test, followed by 10 trials of IM adaptation and test. During the pre-test, the signal dots of the RDK moved left or right. During IM adaptation, 10 randomly selected images depicting leftward (or rightward) IM were presented. In the test, the RDK was presented immediately after the last IM image. An observer, blinded to the motion direction, assessed the OKN direction. The number of matches in OKN responses for each RDK direction was calculated as the match ratio of OKN. We conducted a two-way mixed analysis of variance, with age group (5-6 months and 7-8 months) as the between-participant factor and adaptation (pre-test and test) as the within-participant factor. Only in 7-8 months the OKN responses were shifted in the opposite direction of RDK by viewing a series of images depicting motion, and these infants could detect both IM and RDK motion directions in the pre-test. Our results indicate that detecting the IM and RDK directions might induce direction-selective adaptation in 7-8 months.

Retinotopy drives the variation in scene responses across visual field map divisions of the occipital place area.

The occipital place area (OPA) is a scene-selective region on the lateral surface of human occipitotemporal cortex that spatially overlaps multiple visual field maps, as well as portions of cortex that are not currently defined as retinotopic. Here we combined population receptive field modeling and responses to scenes in a representational similarity analysis (RSA) framework to test the prediction that the OPA's visual field map divisions contribute uniquely to the overall pattern of scene selectivity within the OPA. Consistent with this prediction, the patterns of response to a set of complex scenes were heterogeneous between maps. To explain this heterogeneity, we tested the explanatory power of seven candidate models using RSA. These models spanned different scene dimensions (Content, Expanse, Distance), low- and high-level visual features, and navigational affordances. None of the tested models could account for the variation in scene response observed between the OPA's visual field maps. However, the heterogeneity in scene response was correlated with the differences in retinotopic profiles across maps. These data highlight the need to carefully examine the relationship between regions defined as category-selective and the underlying retinotopy, and they suggest that, in the case of the OPA, it may not be appropriate to conceptualize it as a single scene-selective region.

The effects of combining visual-auditory stimuli with exercise on short-term affect improvement: a randomized controlled trial.

ABSTRAC T: Prior research has explored the effects of engaging with real or virtual natural landscapes and listening to music during aerobic exercise on short-term affect, however, the specific differences in the improvement of short-term affect by different combinations of Virtual Reality (VR) and music rhythm require further investigation. The objective of this study is to investigate the effects of various combinations of VR and music on short-term mood, thereby providing a reference for future research on public fitness. This study recruited 132 valid participants (mean age 24.0 ± 0.9 years), with a gender distribution of 68 males and 64 females. Participants were randomly assigned to one of four groups: Visual-Music (V-M), Music-Visual (M-V), Visual-only (V), and Music-only (M). The exercise mode was 15 min of aerobic power cycling with 2 min of low-intensity power cycling intervals in the middle. After the exercise, the participants were asked to sit and then performed either a VR intervention or a music intervention for 15 min. The collected indicators included blood pressure, positive/negative affect, and heart rate variability indicators (RMSSD, SDNN, LF/HF). Data analysis included descriptive statistics, repeated measures ANOVA, and multifactor ANOVA. The effect of different VR and Music combined with exercise interventions on the improvement of short-term affect was analyzed based on the effect size (ɳp2) and combined with the significance p-value. Intra-group results showed that DBP, positive and negative affect, SDNN, RMSSD indicators in V-M group were significant differences (p < 0.05), while SBP, positive affect, negative affect, SDNN, RMSSD, LF/HF indicators in M-V group were significant differences (p < 0.05). Only SDNN and RMSSD indicators in M group had significant differences (p < 0.05), and only SBP and RMSSD indicators in V group had significant differences (p < 0.05). The results between groups showed that only SDNN and LH/HF groups had a significant difference (p < 0.05), other indicators had a trend of improvement or positive promotion to a certain extent, but the statistical difference was not significant (p > 0.05). Aerobic exercise with consistent intensity and the combined visual-auditory interventions (M-V and V-M) significantly improved blood pressure, and the short-term affect of physiological responses (LF/HF, SDNN, RMSSD), along with subjective affect measures, compared to other groups. These findings suggest that incorporating VR and music with exercise can effectively enhance short-term affect, recommending an integrated approach to aerobic exercise and relaxation through music and visual exposure to natural environments.

Moving spiders do not boost visual search in spider fear.

Previous research on attention to fear-relevant stimuli has largely focused on static pictures or drawings, and thus did not consider the potential effect of natural motion. Here, we aimed to investigate the effect of motion on attentional capture in spider-fearful and non-fearful participants by using point-light stimuli and naturalistic videos. Point-light stimuli consist of moving dots representing joints and thereby visualizing biological motion (e.g. of a walking human or cat) without needing a visible body. Spider-fearful (n = 30) and non-spider-fearful (n = 31) participants completed a visual search task with moving targets (point-light/naturalistic videos) and static distractors (images), static targets and moving distractors, or static targets and static distractors. Participants searched for a specified animal type (snakes, spiders, cats, or doves) as quickly as possible. We replicated previous findings with static stimuli: snakes were detected faster and increased distraction, while spiders just increased distraction. However, contrary to our hypotheses, spider targets did not speed up responses, neither in the group of control nor in the group of spider-fearful participants. Interestingly, stimuli-specific effects were toned down, abolished, or even changed direction when motion was introduced. Also, we demonstrated that point-light stimuli were of similar efficiency as naturalistic videos, indicating that for testing effects of motion in visual search, "pure" motion stimuli might be sufficient. As we do show a substantial modulation of visual search phenomena by biological motion, we advocate for future studies to use moving stimuli, equivalent to our dynamic environment, to increase ecological validity.